What do <:<, <%<, and =:= mean in Scala 2.8, and where are they documented?

Question

I can see in the API docs for Predef that they\'re subclasses of a generic function type (From) => To, but that\'s all it says. Um, what? Maybe there\'s documentation some

Answer 1

Not a complete answer (others have already answered this), I just wanted to note the following, which maybe helps to understand the syntax better: The way you normally use these "operators", as for example in pelotom's example:

def getStringLength(implicit evidence: A =:= String)

makes use of Scala's alternative infix syntax for type operators.

So, A =:= String is the same as =:=[A, String] (and =:= is just a class or trait with a fancy-looking name). Note that this syntax also works with "regular" classes, for example you can write:

val a: Tuple2[Int, String] = (1, "one")

like this:

val a: Int Tuple2 String = (1, "one")

It's similar to the two syntaxes for method calls, the "normal" with . and () and the operator syntax.